A Technology Platform For the Sustainable Recovery and Advanced Use of Nanostructured Cellulose from Agri-Food Residues (PANACEA Project)

Abstract

The European food sector generates about 250 million tons/yr of by-products and waste, of which around 10% from fruit and vegetable processing, with a heavy environmental burden. The agri-food residues (AFR) contain a significant fraction of cellulose and bioactive compounds (mainly antioxidants), which, if recovered, are high added-value material components. The reduction of cellulose down to nano-sized crystalline structures (nanocellulose, NC) provides versatile building blocks, which self-assemble into new materials with superior performances. Despite wood-derived NC is generally considered a green material, its production process is environmentally unfriendly and its large scale utilization would contribute to deforestation. Therefore, more sustainable sources, such as AFR, are desired. The PANACEA project, within the frame of PRIN 2017 call supported by the Italian Ministry of University and Research, proposes an approach based on the recovery of cellulose and bioactive compounds from AFR, with high yield, at various degrees of hierarchical organization, by cascading different physical and chemical processes of increasing complexity. More specifically, physical processes and microbial digestion are exploited to obtain micro-sized cellulose structures while preserving their bioactivity. Chemical and enzymatic processes are used to isolate, purify and functionalize NC at different levels of hierarchical organization, and to design advanced functional materials such as food ingredients, edible coatings, functional colloids, biocides and flame retardants. The sustainable integrated valorization of AFR is addressed through (i) ad hoc pre-treatment of different AFR (Tomato peels, Wheat straw, Coffee residues, Rice bran, Grape marcs, Orange peels), available all year round and with different composition, (ii) application of proprietary high-pressure homogenization (HPH) techniques to micronize the residues in water and completely disintegrate the vegetable cells, with integrated physical fractionation to recover insoluble fibers, (iii) combination with chemical fractionation or high P/T autohydrolysis, or enzymatic treatments. The fabrication of NC structures with tunable size, crystallinity, and surface properties is important to bridge the gap between the production of cellulose and cellulose hybrids and the final applications and is pursued through (i) the size-reduction of NC, or enzymatic lysis, (ii) functionalization via amination or phosphorylation, or (iii) via physical immobilization or covalent bonding with limonene. The characterization of NC in terms of (i) yields, purity, physicochemical, structural, and functional properties, using a multi-technique approach, is associated to the evaluation of (ii) bio-accessibility (through the simulated digestive process) of bioactive compounds and fibers, (iii) film-forming capacity, (iv) gas-barrier properties, (v) rheological behavior, as well as (vi) energy, water, and reagents consumptions. Finally, the PANACEA project also addresses the exploitation of NC-based colloids for novel materials and applications, such as (i) edible coatings, antimicrobial varnishes, and oil structuring materials, (ii) packaging films with gas-barrier properties, and (iii) fabrics and foams with flame-retardant properties (iv) advanced nanocomposite films, (v) Pickering emulsions, and (vi) antimicrobial films and coatings. The main contribution of the PANACEA project to the advancement of the knowledge is expected in (i) the deployment of greener and sustainable, cascading processes exploiting raw AFR functionalities, (ii) the tailored valorization of different AFR by developing physical, chemical, and biological procedures for sculpting the nanostructures, and (iii) the development of sustainable, high performing advanced materials such as edible coatings and gas barrier packages for the food industry, foams, and textiles with flame retardant properties, biocides for organic pest control in agriculture.